reply_to_email

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Since no annotations are provided, the description carries the full burden of behavioral disclosure. It only says 'Reply to an existing email' without stating whether this sends the reply immediately, creates a draft, requires authentication, modifies the original email, or how threading and attachments are handled.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is one short, front-loaded sentence with no filler. It is efficient and easy to parse, though it sacrifices behavioral context that would have made it more useful.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

With no annotations and no output schema, the description needs to supply behavioral and selection context, but it does not. The agent is left to infer what 'reply' means operationally and how it differs from send_email, despite the schema covering the parameters well.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

All four parameters are fully described in the input schema, including the nuance about mailbox and UID uniqueness. The description adds no additional parameter meaning, but with 100% schema coverage the baseline of 3 is appropriate.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description states a specific verb and resource: 'Reply' to 'an existing email'. This clearly communicates the core operation and, at a basic level, distinguishes it from composing a new email via send_email. However, it does not name the sibling alternative explicitly or add scope details.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

There is no explicit guidance on when to use this tool versus send_email or other siblings. The phrase 'existing email' implies a precondition, but the description never states when to prefer this tool, what inputs are prerequisites, or how it differs from related tools in the sibling list.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.